Process for the production of porous bodies



CUWUEEUUNS,

iNG PLASTIC Patented Mar. 20, 1945 UNITED STATES Examiner PATENT OFFICEPROCESS FOR THE PRODUCTION OF POROUS BODIES Josef Schneider, Oberurselin Taunus, Germany; vested in the Alien Property Custodian No Drawing.Application February 28, 1941, Sc rial No. 381,191. In Germany January4, 1940 having a vesicular structure, and more particularly to solidporous bodies for building purposes. Hitherto it was known to producethe cellular structure of solid porous bodies by gas generation I in apaste containing hydraulic binders, such as cement, gygfsy% or the like,and, if desired, also filling ma la e. g., sand, textiles or the like.The gas generation has been accomplished bythe sgls before the mixtureis cast into the molds, contrary to the hitherto lniowiifrietliodswfir'eit was necessary to cast the paste into the molds as quickly as possiblewhereby the gas generation was accomplished in the molds. Since it isnot necessary to form the mass in the mixing vessels the charges may beconsiderably enhanced.

Moreover, the molds into which the mass, in

which the gas generation has already taken place,

add t n of aseous. oxy en evolving gognpoung I0 is cast, maLbe filled upto the brim since the like hydrogenperoxide, In order to reduce the costof the production, hymchloriteswere sometimes added which, in thepresence of peroxygen compounds, liberated their active oxygen. In-

volume of the masswm o 'be increased by any subsequent gas generation.In this manner any losses of material will be prevented which hithertowere quite unavoidable because the measure stead of hypochlorites, deomposition.catalysts, of the last rising could not exactly be foreseenfor example compounds of the heavy metals, e. g., manganese sulfate,have also been used. And finally it was also known to stabilize thepores f rmed y the gas. ni rai lm.ailhfilllli ll liia bi.

and it was necessary normally to fill the molds so that they containedan excess of material which afterwards was stricken oil? and cast away.

According to another embodiment of myinaddingsubstanceswhichreduccdthesuriaaaicnr vention only a part oitheeneratin a ent for sion such as soap, glue or the like, in order toprevent wasteful escape of the oxygen evolved and to prevent partialreduction of the risen paste.

To obtain satisfactory results in the manufacture of the gas generatingmixture it was heretofore necessary to observe a pre-determined orderwith respect to the addition of the components to the mixture. A pastewas made from cement, water, stabilising substances, hydrogen peroxideor other peroxygen compounds, and then if desired, filling materialssuch as sand and finally introducing an accelerator for thedecomposition 01 the peroxygen compounds, for example, hypochlorite.This procedure succeeded in a slow gas generation which lasted severalhours which produced very fine gas bubbles at the beginning. The paste,homogenized during the rising process, was then cast into the molds and,avoiding any percussion, allowed to stand until the gas generation hadfinished.

Now I have found that the rising of the paste may substantially beaccelerated without causing the escape of considerable quantities of theoxy: gen generated from the paste if the pore stabilising substance isintroducedfirfill g Itgi fijeia'fisl? ess a 2 ya Sifice cement exerts amlising effect on the peroxygen compounds and consequently delays thegas generation process it has proved advantageous for the preparation oflight concrete 9.0- 50 pose substancesswitfi a refluc ng egect on thecording to my invention, first to mix cement, surfacetension may beused," for instancew water, hypochlorite and filling materials after lueTurke red oil, tar oil e. g. which thepore stabilising substance isadded ar oil o a rac mm between IOU-300 C. as. w. l simultaneous y w e yrogen peroxide. Im- 55 g as generation g f the mass in the mixing ves-25 stabilising agent are added to the mixture of cement, water and filliaterials Before the accelerator for the decomposition oi the hydro- "genperoxide, for example, hypochlorite, is introduced. In practicing thismethod the first art of the h dro en eroxide which was added fie ore thehypochlorite is Introduced, is stabilised by Wat present whilst thesecond and later addedpart of the hydrogen roxi e is ecomg pg sedaiidliberates oxygen i'mmeaiafily after the adm x ure e paste. Thus veryfine bubbles are formed which serve as nuclei for the gas beginning tobe generated from the first slowly decomposing part of hydrogenperoxide.

According to my invention it is possible to obtain bodies with eitherfine or coarse vesicular structure by careful measurement of thequantitative portions of the hydrogen peroxide added in two operationsteps. The greater the portion of the first added quantity of hydrogenperoxide,. the coarser the pores in the structure of the final product.

Another means forlfluaminstbaa w Of t pomsllas been found in theselection and quantity of the stabilising substance. For this purofpores on t gyntity of rnilk added was obas products which are obtainedby an alkaline .gxtraction of wood pitc and subsequently conserved.Reducing .the quantity gf milk increases the size of the pores. The samelaws could be observed in adding saponine and other stabilizers, but notto the same degree as in adding milk. If, for instance, 5 cc. of skimmilk are added to a mixture of about 1 kilogram cement and sand whichrepresents an amount of 0.5% milk, a very fine porous structure wasobtained whilst an addition of 0.3 to 0.2% of milk increases the size ofthe pores in a considerable manner. According to my invention itjstherefore pgssible s' 'iiiilljaadedi teasers! mixtum, wherbfthe 1-129 isintroduced in a'twdstep prdess to 'obtain well reproducible bodisWith aprede named size of pores."This"ls;"of"course, Vrylmportantinlarge scaleproduction. A further advantage of the addition of milk anglor saponineis that both components may be'wll mlx'ed wlth a solution of hydrogenperoxide. It is therefore expedient to add a solution of sapoof aHomogeneous v nine in h%drogen peroxide mix ure 0 mil an ro en eroxideto the ul and then distribute the added substances in Elie pulp whichwarrants that in the place where hydrogen peroxide is decomposed andoxygen evolved, the suitable quantity of the pore stabilizer will bepresent.

All operation steps described above for cement mixtures are alsoapplicable to other substances, hardening with water, as for instance,sum. But since gypsum exerts no stabilising e ect on peroxygencompounds, the whole quantity of the gas generating substance, forexample, hydrogen peroxide, may be added without any deleterious efiectbefore the decomosition acceleratin substances e. g., It h ochlorite ndthe like, are introduced. It is only essential that the Fore stabilizeris added at theend of the opera ion eit er s ultan'eously'o'r admixed toone of the substances which participate at the oxygen generation, thatis either with the gas generator such as hydrogen peroxide decom osinwit a substance for instance, ypochlolike.

Example 1 375 cc. of a calcium hypochlorite suspension (100 gramshypocfilorite with nearly 31% active chlorine, suspended in 150 cc.water) are intimately mixed with 2200 cc. of water 800 grams of andflessthan 1 mm. mesh; and 3200 grams of Portland cement. To this mixture 90cc. of a solution contaimng 50 cc. of a 40% hydrogen roxi 4 cc. skimmilk and 1.5 grams's'EBFrTn'E are added. After a thorough mixing the gasgeneration starts immediately whereupon the original paste rises to amultiple of its former volume. If the pulp is immediately poured out, aslight increase of the volume will be observed in the mold, whilst nomodification of the volume ocurs if the foam is allowed to stand for aquarter of an hour. Porous bodies will then be obtained which correspondaccurately to the prescribed form. In this manner bodies with anabsolutely uniform porous structure are obtained.

Example 2 oxide solution with 4.5% sa nine are added and the wholemixture vigorously stirred. Then a ill sus ension of 3'75 cc. of acalcium hypgchlgritg solution (according to Example and finally 75 cc.of a 40% hydrogen peroxide solution with 4.5% saponine are added and thepastetho'f'ough- 13' mixed. m

Example 3 To a mass of concrete which contains 210 cc. water 730 gramssang with a size of 0.3 mm. mesh and 312 grams of w l n e 2 cc. of a 40%h dr e e and 25 cc. of a calcium hypoc drlte susgnsion (including 400grams of 0.8 liters water are intimately mixed with cc. of asodium'hypochlorite solution (11% active chlorine) arfiwgrams commercialum added until a homogeneous paste is formed. Ifi this paste 6 cc.hydrogen peroxide (40%) with 0.3 gram sapgnine are ncorporated. Itresults in the instan aneous development of foam with the formation ofvery small stable pores. After casting into the molds, articles with anapparent specific gravity of 0.28 are obtained.

Example 5 6cc .mz-iu H are added to a mass of 800 cc. water and 870grams sum To this mixture a suspension of 5 grains rolusite in 5 cc. ofan a ueous solutio of 4% sapo'nine is added, the whole mass wellhomogenized until the gas evolution is practically ended. It results ina very stable froth. The molds may be filled out completely and nofurther increase of volume will be observed.

Example 6 Into a mass of 800 cc. water and 870 grams of gypsum, 6 cc.hydrogen roxid (40%) are addra" ed whilst stirring. 'Ifien i cc. of asolution cont ,1

taining 2 grams of c stallized man an 1- fate in cc. of water and 10 cc.skim milk are incorporated, whereupo'n 1.7 cc. of a concentrated ammoniasolution are added and the whole mass oroug ly s irre The wellhomogenized paste is cast into molds whereupon the gas generation startswith an increase of volume. It results in an article with anextraordinarily fine-vesicular structure.

Example 7 The same composition as in Example 6 is prepared but with theaddition of 5 cc. k only. A solid porous body with a coarse-vesicularstructure is obtained.

What I claim is:

The method of controlling the development of gas pores in the productionof cellular cementitious bodies which consists in mixing cement, afiller and water with a portion of hydrogen peroxide and of an oxygenstabilizing agent selected from the group consisting of skim milk andsamnine, adding the remainder of the required peroxide and stabilizingagent after the initial development of gas and finally adding analkaline hypochlorite to produce a second development of stabilized gasbubbles smaller than those first produced.

. JOSEF SCHNEIDER.

